This summer, Derek McLennan was given £1.98 million for the hoard of Viking jewellery he'd unearthed three years earlier, and last month Mike Smale unearthed a cache of 2,000-year-old Roman silver coins worth £200,000 in a Dorset field.

Finding treasure usually requires a bit of investment on your part - you'll need a metal detector, costing anywhere from £30 or so up to more than £1,000.

And if you want to search on land that isn't yours, you'll need the permission of the landowner.

But what happens if you're lucky enough to find something valuable? What should you do, and what are your rights?

Under the 1997 Treasure Act, there's a tight definition of what counts as treasure.

Any metallic object, other than a coin, is treasure, as long as at least 10% by weight of metal is gold or silver and that it's at least 300 years old when found.

So, too, are two or more coins from the same find, again provided they are at least 300 years old when found and contain 10% gold or silver; and any group of two or more prehistoric metallic objects.

If you're lucky enough to find anything like this, you'll need to report it to the local coroner. The Treasure Valuation Committee will then decide what it's worth, and if a museum wants to buy it you'll share the proceeds with the owner of the land where it was found. The money is usually split 50:50.

As for where to look, Norfolk is the county where the most valuable finds have been made - 1,292 of them.

They include the Snettisham Hoard - a large collection of Iron Age gold torcs and coins found between 1948 and 1973. Other finds include Anglo-Saxon, Roman and Civil War coins.

And this time last year, an Anglo-Saxon gold pendant inlaid with garnets was declared treasure, after being described as 'something of major significance'.

If you want to know whether treasure has been found near to you, online casino PartyCasino has created a tool to help.

Plug in your postcode, and it will retrieve all the artefacts found nearby, complete with descriptions and images.

There are lots of groups and societies devoted to metal detecting, and the chances are there's one near you - there's more information here.

"The many thousands of metal detectorists who enjoy this fascinating pastime reap benefits in a variety of ways; relaxation away from the pressures of work or domestic life, fresh air and exercise, and making new friends and meeting other enthusiasts," say the experts at UK Detector Net.

"But these are common to many other hobbies and there are more particular benefits which set metal detecting apart; the coins and artefacts recovered, the excitement and pleasure one feels when handling them for the first time, and the inevitable gain in knowledge of our past."